Abstract:

The development of metal-ion batteries with enhanced performance is critical to meet the requirements of electric vehicles and energy storage grids. The energy density of conventional battery electrodes is limited by the added electrochemically inactive components: PVdF binder and carbon black conduit, which make up significant fraction of the electrodes. Alternative binders and conducting agents such as conducting polymers and carbon nanomaterials attract growing attention for the development of high energy density battery electrodes.

In this contribution, a variety of novel electrically conductive polymer binders including PEDOT-based polymer complexes and polymer / carbon nanotubes (CNTs) composites are discussed. Special attention is paid to fluorine-free polymer binders, that are processed through environmentally benign solvents. The developed binders were used for formulation of high energy density lithium iron phosphate cathodes for Li-ion batteries.

We report that using polymer/CNTs composite binders allows to increase the content of electrochemically active material (95 wt.% of LiFePO4) and cathode energy density while maintaining high stability and cyclability. The electrical conductivity and rate capability of the electrodes are influenced by the polymer-to-CNTs interactions, being higher for polyacrylonitrile and sulfonated polymers as compared to PVdF. Cycling stability of the developed cathodes is strongly affected by the interfacial affinity of the polymer binder to Al current collector, as observed by peel-off adhesion tests. The highest adhesion strengths correspond to cathodes formulated with PVdF and polyacrylonitrile binders.

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Acknowledgments: The authors acknowledge financial support from the Russian Science Foundation (project 17-73-30006).